The invention relates to a hand-held apparatus for cutting transversely a hollow cylindrical object such as a pipe, particularly suitable for situations in which the said pipe is not easily accessible and in which it is difficult to insert conventional cutting tools; in particular, the invention can be used in the automotive field, for example for cutting a pipe forming all or part of a car exhaust system.
The professionals concerned are well aware of the difficulties of disassembling a car exhaust pipe during a repair or a replacement; it is very frequently impossible to disassemble or replace it, consequently it is often necessary for example to make a clean cut on an intermediate pipe if the intermediate pipe is still sound and to connect it with a spare part provided for it.
It is always difficult to cut a hollow cylindrical object in that it is difficult to make genuinely transverse cuts, in other words perpendicular to the center line of the pipe, and furthermore a clean well-defined cut cannot be made unless the saw is held correctly; obviously, this needs special know how and in particular sufficient space is necessary around the part to perform this operation correctly.
It is easily understandable that in cases such as a car exhaust pipe when the cut has to be made on the car itself, it is not easy to use tools such as saws, particularly if a fairly precise cut is necessary.
Another method that has been known for a long time makes use of tube cutting tools that operate by sawing and by cutting around the periphery, in which the groove depth is gradually increased by rotating the tool around the pipe within the transverse cutting plane; this type of tool usually comprises an annular casing that is placed around the pipe approximately in the cutting plane; this casing comprises a slitter that is tangential to the pipe on the cutting line and is rolled around the periphery of the pipe, the axis of rotation of the cutter remaining parallel to the center line of the pipe; two symmetrical arms spreading out radially from the annular casing of the pipe, firstly to rotate the said casing when the slitter is in contact with the pipe, and one of them is usually equipped with a strip of screws enabling an appropriate mechanism to push the center line of the slitter radially towards the pipe in order to increase the cutting pressure on the pipe as the slitter rotates; obviously, counter-reaction devices with rollers are provided to center the pipe in the annular casing, for which they facilitate rotation movements around the pipe. Obviously, this type of apparatus is completely unusable in cases in which the environment around the pipe is not sufficiently clear to enable free rotation of the arms controlling the rotation torque or the cutting pressure on the slitter, as described above.
Therefore, the purpose of the invention is to propose improvements to a hand-held apparatus for making clean and precise pipe cuts under conditions with difficult access, in other wards giving preference to the cutting technique rather than sawing techniques, as mentioned in the preamble, to overcome the disadvantages mentioned. In this respect, the manual apparatus for transverse cutting of pipes according to the invention using a hand-held apparatus for transverse cutting of a pipe using at least one slitter rolling around the external surface of a pipe in the transverse cutting plane and to which an approximately constant radial pressure is applied in cooperation with counter reaction rollers to provide a deepening cut until the pipe has been completely cut, is remarkable in that the apparatus is formed of two half-shells mounted around the pipe by clamping means adjustable in the cutting plane with internal concave faces facing each other, one of which supports at least one slitter installed at the same distance from each end of the half-shell and free to rotate around an axis perpendicular to the cutting plane and that may be fixed or free to move parallel to the cutting plane along the radial direction of the apparatus such that the cutting part projects radially beyond the internal surface of the half-shell by a value equal to or greater than the thickness of the pipe, and the other supports either at least two rollers that are advantageously identical mounted to project beyond the shell like on the second half-shell and distributed on each side at equal distances from the ends of the said half-shell, or at least two rollers free to rotate around two fixed axes perpendicular to the cutting plane so that their rolling surface projects radially from the inner surface of the half-shell and each axis is the same distance from the closest end of the half-shell, the slitter(s) all being in the same cutting plane, the rollers on the same half-shell being laid out in pairs facing each slitter on the other half-shell to compensate for the cutting force as the assembly rotates together around the pipe in the cutting plane, obtained by cooperation of a driving tool with catching means distributed on the external surface or around the periphery of each half-shell. An apparatus of this type is described in U.S. Pat. No. 3,163,932 in which the half-shells are hinged at one end and are provided with a quick fastener system to close them at the other end; obviously, this apparatus is limited to cutting a pipe with a particular diameter, since the width of the passage between the slitter and the roller is fixed during manufacture.
Furthermore, this special tooling is particularly expensive to manufacture.
According to the invention, each half-shell of the apparatus has the same general shape obtained starting from a flat with an appropriate thickness, for example made of steel plate, cut out and stamped in the general shape of a ring with a vertical axis of symmetry in its plane, and a recess in the center of the ring being provided into which the largest sections of the pipe to be cut can be fixed, and its periphery being cut out as a function of the profile of the driving tool catching means such that the right side and left side of the vertical axis of symmetry of the ring can be made to correspond by orthogonal projection after the ring has been put in a general shape of a U by rectangular double folding around two vertical center lines parallel to the said vertical axis of symmetry and placed at equal distance from it, thus forming a cap for the cutters and/or the rollers after suitable folding and drillings, the top and bottom parts of the ring between the two folding lines corresponding to the bottom of the U and forming connecting parts between the left and right parts of the cap, and being designed to be fitted with adjustable means for tightening the two half-shells after assembly facing each other on opposite sides of the pipe.
It is easy to understand all the advantages of this type of apparatus which combines performances to be expected from the most highly professional apparatus, to the simplicity and the sturdiness well adapted to the function of the tool. In this respect, it is easy to understand the operation of this device that comprises two symmetrical assemblies that are simply placed on each side of the pipe to be cut and fixed in position opposite each other with their ends facing each other, as will be described later. In this case, it will be noted that the only environmental clearance limit is approximately equal to the greatest thickness of each half-shell, so that the most difficult (or almost) cases can be handled.